Wireless power transmission apparatus for induction heating and control method thereof

ABSTRACT

A wireless power transmission apparatus for induction heating includes: a working coil configured to change operation based on selection of a mode of operation from among a plurality of operating modes, the plurality of operating modes including a wireless power transmission mode configured to wirelessly transmit power and a heating mode configured to heat one or more objects, an inverter configured to output, to the working coil, current at an operation frequency, and a controller. The controller is configured to receive, in the wireless power transmission mode, a load voltage from a target object, compensate for the load voltage, and determine, in the wireless power transmission mode, whether a foreign object is present in the working coil based on the compensated load voltage.

CROSS-REFERENCE TO THE RELATED APPLICATION

The present disclosure claims priority to and benefit of Korean PatentApplication No. 10-2020-0024272, filed on Feb. 27, 2020, in the KoreanIntellectual Property Office, the disclosure of which is incorporatedherein by reference in its entirety.

TECHNICAL FIELD

The present disclosure relates to a wireless power transmissionapparatus, and more particularly, to a wireless power transmissionapparatus for induction heating and a control method thereof.

BACKGROUND

Wireless charging refers to a method of charging a device by wirelesslytransmitting power through the atmosphere instead of a method ofcharging a device by transmitting power through a wire.

According to the basic principle of wireless charging, when alternatingcurrent (AC) flows into a transmission coil, a battery is charged byforming a magnetic field around the transmission coil, allowing AC toflow in a reception coil due to influence of the magnetic field, andrectifying the AC.

Various small-size kitchen utensils are used in a kitchen, that is,small home appliances require power supply, and thus, the appliancesreceive power by connecting an electric cord (power connection cable)that is separately included in the appliances to a socket. In this case,there is a problem in that a plurality of electric cords adverselyaffects management, safety, or space utilization.

Thus, recently, the demand for wireless power charging of small homeappliances used in a kitchen has rapidly increased.

For example, devices that need to be heated using induced current amongthe small home appliances have increasingly been spread.

Such a heating device using induced current uses an induction method ofheating the device via electron induction by generating a magnetic fieldand is operated in the same way as an electric range.

For example, a general electron induction heating device allowshigh-frequency current to flow in a working coil or heating coilinstalled therein.

When the high-frequency current flows in the working coil or the heatingcoil, a strong line of magnetic force is generated. The line of magneticforce generated in the working coil or the heating coil forms eddycurrent while being transmitted through a cooking tool. Thus, as eddycurrent flows in a cooking tool, heat is generated to heat a containeritself, and materials in the container are heated as the container isheated.

As such, there is the increasing demand for a multi-functional wirelesspower transmission device that is capable of performing wirelesscharging as well as induction heating depending on a type of the smallhome appliance.

The multi-functional wireless power transmission device is capable ofperforming induction heating or wireless power transmission by changinga frequency using one working coil or heating coil according to a modeselected by a user.

When induction heating or wireless power transmission is performed on atarget small home appliance of the multi-functional wireless powertransmission device, it is required that a reception coil and workingcoil of the target small home appliance are aligned with each other.

That is, when the two coils that perform wireless power transfer are notaligned with each other and are eccentrically arranged, powertransmission efficiency is remarkably lowered.

To this end, technologies of determining eccentricity and providing analarm therefor or compensating for this in wireless power transfer areproposed.

For example, a conventional battery charging system for a vehiclethrough wireless power transfer is introduced, which discloses thatinformation regarding a charging state of a reception side is received,and when a charging state value is less than a reference value, analignment state is adjusted by moving a coil of the reception to achievea constancy state.

However, for the conventional battery charging system, it is required tochange the coil of the reception side for alignment. However, in thecase of wireless power transfer of a small home appliance, it isrequired to continuously provide an alarm to a user to match a state oftransmission/reception coils with constancy, and alignment state matchis a factor that impedes use convenience of a wireless small homeappliance.

A conventional device including a magnetic component at a reception sideis introduced to solve such problem. For example, the magnetic componentis automatically aligned with a transmission coil by allowing DC currentto flow when an alignment state of transmission/reception coils is notmatched in a wireless power transmission system.

As such, when a reception coil includes a magnetic component, a metallicforeign object may be attached thereto together, and thus, there is arisk of ignition or fuming due to a magnetic field generated duringwireless power transfer.

In addition, it is also required to detect whether a foreign object ispresent between a target object and a working coil, to provide an alarmthereof, to remove the foreign object, and then to transmit power.

When a foreign object is present, there is a problem in terms ofdegradation in power transfer, and a risk of ignition depending on amaterial of a foreign object is inherent.

To this end, a conventional wireless power transmission apparatus isconfigured to detect a foreign object. According to the conventionalwireless power transmission apparatus, a signal generating circuit isconfigured to generate a detection signal of a specific frequency andreceives a signal to generate a magnetic field in a source coil, andwhen a foreign object is present in a source coil, a detection coildetects the signal and transmits the signal to a controller.

That is, in order to detect a foreign object, a plurality of detectioncoils is additionally required, and there is an additional need for asignal generating circuit for detection. Thus, there is a need for aseparate auxiliary circuit that consumes costs and space.

A conventional detection method discloses that a variation amount of aresonance frequency is calculated to detect a foreign object, andincrease in the resonance frequency due to reduction in inductancegenerated when a foreign object is present is detected. Thus, whether aforeign object is present is determined via change in the resonancefrequency.

However, in the case of a conventional mobile charging system, atransmission coil has a small size, and a change in frequency due to animpedance difference is easily detected because impedance is remarkablyincreased when a foreign object is present, but in the case of a homeappliance or a vehicle, a transmission coil has a large size, but avariation in impedance due to a relatively small foreign object isremarkably reduce, and thus, there is a limit in determining whether aforeign object is present.

SUMMARY

According to one aspect of the subject matter described in thisapplication, a wireless power transmission apparatus for inductionheating includes a working coil configured to change operation based onselection of a mode of operation from among a plurality of operatingmodes, the plurality of operating modes including a wireless powertransmission mode configured to wirelessly transmit power and a heatingmode configured to heat one or more objects, an inverter configured tooutput, to the working coil, current at an operation frequency, and acontroller. The controller can be configured to receive, in the wirelesspower transmission mode, a load voltage from a target object, compensatefor the load voltage, and determine, in the wireless power transmissionmode, whether a foreign object is present in the working coil based onthe compensated load voltage.

Implementations according to this aspect can include one or more of thefollowing features. For example, the controller can operate in apreparation period prior to a normal wireless power transmission modeconfigured to perform wireless power transmission to the target object,and the controller can be configured to determine, in the preparationperiod, whether the foreign object is present in the working coil.

In some examples, receiving the load voltage from the target object caninclude receiving information regarding the load voltage from the targetobject, and compensating for the load voltage can include compensatingfor the load voltage based on a current input voltage. In someimplementations, the controller can be configured to recalculate thecurrent input voltage based on a first reference input voltage, performcompensation for removing variation in the load voltage with respect tothe current input voltage, and calculate the compensated load voltage.

In some implementations, the controller can be configured to (i)compensate for an eccentricity degree between the working coil and areception coil of the target object with respect to the calculatedcompensated load voltage and (ii) calculate a first calculated loadvoltage based on the compensation for the eccentricity. In someimplementations, the controller can be configured to determine whetherthe foreign object is present based on the first calculated load voltagewith respect to the first reference input voltage.

In some examples, based on the foreign object being determined presentaccording to the first calculated load voltage, the controller can beconfigured to: (i) calculate a second calculated load voltage withrespect to a second reference input voltage and (ii) determine whetherthe foreign object is present based on the second calculated loadvoltage. In some examples, based on the first calculated load voltageand the second calculated load voltage being outside a predeterminedrange, the controller can be configured to determine that the foreignobject is present.

In some examples, the predetermined range can include a first range anda second range for the first calculated load voltage and the secondcalculated load voltage, respectively, the first range and the secondrange being different from each other.

In some implementations, the wireless power transmission apparatus canfurther include an upper glass arranged to receive the target object,and an input unit configured to receive the selection of the mode ofoperation.

According to another aspect of the subject matter described in thisapplication, a method of operating a wireless power transmissionapparatus for induction heating, which includes a working coilconfigured to change operation based on selection of a mode of operationfrom among a plurality of operating modes, the plurality of operatingmodes including a wireless power transmission mode configured towirelessly transmit power and a heating mode configured to heat one ormore objects, includes checking whether the wireless power transmissionmode is selected, a preparation operation including (i) receiving, inthe wireless power transmission mode, a load voltage from a targetobject while an inverter output current at an operation frequency, (ii)compensating for the load voltage, and (iii) determining, in thewireless power transmission mode, whether a foreign object is present inthe working coil based on the compensated load voltage, and a normalmode operation including performing wireless power transmission at theoperation frequency to the target object.

Implementations according to this aspect can include one or morefollowing features. For example, compensating for the load voltage caninclude compensating for the load voltage based on a current inputvoltage.

In some examples, the preparation operation can include recalculatingthe current input voltage based on a first reference input voltage,performing compensation for removing variation in the load voltage withrespect to the current input voltage, and calculating the compensatedload voltage. In some implementations, the preparation operation canincludes compensating for an eccentricity degree between the workingcoil and a reception coil of the target object with respect to thecalculated compensated load voltage, and calculating a first calculatedload voltage based on the compensation for the eccentricity.

In some implementations, the preparation operation can includedetermining whether the foreign object is present based on the firstcalculated load voltage with respect to a first input reference voltage.In some implementations, the preparation operation can includes based onthe foreign object being determined present according to the firstcalculated load voltage, calculating a second calculated load voltagewith respect to a second reference input voltage and determining whethera foreign object is present based on the second calculated load voltage.

In some examples, the preparation operation can include based on thefirst calculated load voltage and the second calculated load voltagebeing outside a predetermined range, determining that the foreign objectis present. In some examples, the predetermined range can include afirst range and a second range for the first calculated load voltage andthe second calculated load voltage, respectively, the first range andthe second range being different from each other.

In some implementations, the preparation operation can includecalculating a deviation in the load voltage with respect to a firstreference input voltage based on data of the load voltage received fromthe target object, the data including a variation in a input voltagewith respect to a specific operation frequency, and calculating thecompensated load voltage based on a function between the deviation inthe load voltage and the input voltage. In some implementations, thepreparation operation can include compensating for a value of resonancecurrent with respect to the first reference input voltage, calculatingthe deviation in the compensated load voltage with respect to aneccentricity degree, and calculating last load voltage according to afunction between the compensated resonance current and the deviation inthe compensated load voltage.

In some examples, the method can further include based on the foreignobject being determined present in the preparation operation, providinga user alarm and stopping an operation of the inverter.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram illustrating an upper perspective view of anexemplary wireless power transmission apparatus for induction heating.

FIG. 2 is a diagram illustrating a cross-sectional view of the exemplarywireless power transmission apparatus for induction heating of FIG. 1.

FIG. 3 is a circuit diagram for explaining an induction heating state.

FIG. 4 is a circuit diagram for explaining wireless power transfer (WPT)of an exemplary wireless power transmission apparatus for inductionheating.

FIG. 5 is a diagram illustrating a configuration of a target object at areception side.

FIG. 6 is a state diagram illustrating an alignment state between areception coil and a working coil.

FIG. 7 is a schematic flowchart illustrating an exemplary process for amode of a wireless power transmission apparatus for induction heating.

FIG. 8 is a diagram illustrating a structure of a transmission apparatusand a reception apparatus with respect to the flowchart of FIG. 7.

FIG. 9 is a flowchart illustrating an exemplary operation of determiningeccentricity and a foreign object during power transfer.

FIGS. 10A and 10B are graphs showing a compensation method depending oneccentricity.

FIGS. 11A, 11B, and 11C are graphs showing eccentricity compensation.

DETAILED DESCRIPTION

FIG. 1 is a diagram illustrating an upper perspective view of anexemplary wireless power transmission apparatus 10 for inductionheating. FIG. 2 is a diagram illustrating a cross-sectional view of theexemplary wireless power transmission apparatus 10 for induction heatingof FIG. 1. FIG. 3 is a circuit diagram for explaining an inductionheating state. FIG. 4 is a circuit diagram for explaining wireless powertransfer (WPT) of the exemplary wireless power transmission apparatus 10for induction heating.

Referring to FIGS. 1 and 2, a target object 1 can be positioned on awireless power transmission apparatus 10. The wireless powertransmission apparatus 10 can heat the target object 1 positionedthereon or can wirelessly transmit power to the target object 1.

The target object 1 can be a small home appliance having a receptioncoil 15, a small home appliance that does not have the reception coil15, a general heating cooking container that is not an electronicproduct, or a foreign object.

The small home appliance having the reception coil 15 can wirelesslyreceive power using the reception coil 15 through the wireless powertransmission apparatus 10 and can perform a main operation using thecorresponding power. For example, the small home appliance can be awireless blender or a wireless oven toaster.

The small home appliance that does not have the reception coil 15 can bea home appliance that is directly heated by generating a magnetic fieldthrough a working coil 12, which is a transmission coil of the wirelesspower transmission apparatus 10, and can be an electronic product thatis not a general cooking container. An example thereof may be a wirelesselectric kettle or a wireless electric rice cooker. The small homeappliance that does not have the reception coil 15 can include a pickupcoil to supply power to a module that requires driving power from aregion for performing a main operation, that is, a region except for aregion that receives heat and performs a function. The pickup coil canbe positioned away from a region corresponding to the working coil 12that is a transmission coil, and can wirelessly receive power and cansupply power to a module, for example, a control module such as acommunication module, an interface, or a display.

The general cooking container may refer to a container including anelectrical resistance component that can be heated by a magnetic field20 generated from the working coil 12 and through which the magneticfield 20 passes. When a material of the cooking container includes anelectrical resistance component, the magnetic field 20 can generate eddycurrent in the cooking container. The eddy current can heat the heatingcontainer, and the heat can be conducted and transmitted to an internalside of the cooking container. Thus, contents in the cooking containercan be cooked.

When a foreign object is positioned at a position of the target object1, the foreign object tends to be a material having an electricalresistance component that impedes wireless power transfer (WPT) and maybe an iron bar such as a spoon or a chopstick.

The wireless power transmission apparatus 10 can function as anelectronic induction heating apparatus or a wireless power transmissionapparatus according to user's selection.

For example, the wireless power transmission apparatus 10 can functionin an induction heating mode for heating a general heating container orcan function in a wireless power transmission mode for wirelesslytransmitting power to a small home appliance that has or does not havethe reception coil 15 with respect to one working coil 12 according tothe user's selection.

The multi-functional wireless power transmission apparatus 10 caninclude an upper glass 11 and a casing including at least on workingcoil 12, as shown in FIG. 2. First, components included in the wirelesspower transmission apparatus 10 will be described in detail.

The upper glass 11 can protect an internal part of the wireless powertransmission apparatus 10 and can support the target object 1. Forexample, the upper glass 11 can be made of tempered glass of a ceramicmaterial obtained by synthesizing various minerals. Thus, the upperglass 11 can protect an internal part of the wireless power transmissionapparatus 10 from the outside. The upper glass 11 can support the targetobject 1 positioned thereon. Thus, the target object 1 can be positionedon the upper glass 11.

The working coil 12 can wirelessly transmit power to the target object 1depending on the type of the target object 1 or a user mode selection,or can generate a magnetic field for heating, and at least one workingcoil 12 can be configured according to a design. In someimplementations, a region in which the target object 1 is disposed canbe determined depending on each coil 12.

A user input unit for determining a mode of the wireless powertransmission apparatus can be disposed at one side of the upper glass11.

For example, the working coil 12 can be disposed below the upper glass11. Current may or may not flow in the working coil 12 depending onpower on/off state of the wireless power transmission apparatus 10. Whencurrent flows in the working coil 12, the amount of current flowing inthe working coil 12 can also vary depending on the mode and output ofthe wireless power transmission apparatus 10.

When current flows in the working coil 12, the working coil 12 cangenerate the magnetic field 20. As the amount of current flowing in theworking coil 12 is increased, the generated magnetic field 20 can alsoincrease.

A direction of the magnetic field 20 generated by the working coil 12can be determined depending on a direction of the current flowing in theworking coil 12. Thus, when alternating current (AC) flows in theworking coil 12, the direction of the magnetic field 20 can be convertedby a frequency of the AC. For example, when AC of 60 Hz flows in theworking coil 12, the direction of the magnetic field can be converted 60times per second.

A driving module that is electrically connected to the user input unitand the working coil 12, can receive a voltage and current from acommercially available power source, can convert the received voltageand current, and can supply power to the working coil 12 according touser input. In some implementations, the driving module can be disposedin the casing.

In some implementations, the driving module can be a plurality of chipsinstalled on one printed circuit board. In some implementations, thedriving module can be one integrated chip.

The wireless power transmission apparatus 10 can include ferrite 13 thatcan protect the driving module.

For example, the ferrite 13 can function as a shield that blocksinfluence of the magnetic field generated by the working coil 12 or anelectromagnetic field generated outside of the working coil 12 on thedriving module in the wireless power transmission apparatus 10.

To this end, the ferrite 13 can be made of a material with very highpermeability. The ferrite 13 can guide the magnetic field introducedinto the wireless power transmission apparatus 10 to flow through theferrite 13 rather than being discharged.

In some implementations, the wireless power transmission apparatus 10can include at least one working coil 12. In some implementations, thewireless power transmission apparatus 10 can include more than oneworking coils 12.

The respective working coils 12 can have different sizes, and current ofspecific frequency can flow in each working coil 12 throughinverter-driving under control of the driving module, and thus, in theinduction heating mode, target power corresponding to a firepower levelselected by a user can be generated and heat corresponding to the targetpower can be generated.

In the wireless power transmission mode, current of differentfrequencies can flow through inverter-driving under control of thedriving module, and thus, power can be wirelessly transmitted to a smallhome appliance.

To this end, the respective working coils 12 can be connected toinverters in the driving module, and the plurality of working coils 12can be connected in parallel or series to each other by a switch and canbe connected to an inverter.

When the corresponding wireless power transmission apparatus 10 isoperated in the induction heating mode according to user selection, amagnetic field can be generated by current of a predetermined frequencyand can be transmitted through a heating container positioned on theupper glass 11.

In some implementations, when an electrical resistance component isincluded in a material of a cooking container, the magnetic field cangenerate eddy current in the cooking container. The eddy current canheat the cooking container, and the heat can be conducted andtransmitted to an internal side of the cooking container. Thus, theinduction heating mode can proceed in a method of cooking contents inthe cooking container.

Movement of the magnetic field generated in the working coil 12 by theferrite 13 is shown in FIG. 2.

With reference to a circuit diagram in which the wireless powertransmission apparatus 10 is operated in the induction heating mode, thewireless power transmission apparatus 10 can have a structure shown inFIG. 3.

For example, FIG. 3 is a circuit diagram of a wireless powertransmission apparatus in an electromagnetic induction heating mode whenthe wireless power transmission apparatus includes an inverter 140 andan working coil 12 (hereinafter, referred to as 150). The wireless powertransmission apparatus 10 in the electromagnetic induction heating modecan include a rectifier 120, a direct current (DC) link capacitor 130,an inverter 140, the working coil 12 (150), and a resonance capacitor160.

An external power source 110 can be an alternating current (AC) inputpower source. The external power source 110 can supply AC power to anelectromagnetic induction heating cooking device. For example, theexternal power source 110 can supply AC voltage to the rectifier 120 ofthe electromagnetic induction heating cooking device.

The rectifier 120 can be an electrical circuit for converting AC into DCand can convert AC voltage supplied through the external power source110 into DC voltage. In some implementations, opposite ends of DC outputthrough the rectifier 120 can refer to DC links. A voltage measured atthe DC opposite ends can refer to a DC link voltage. When a resonancecurve is not changed, output power can be varied depending on a DC linkvoltage. The DC link capacitor 130 can function as a buffer between theexternal power source 110 and the inverter 140. For example, the DC linkcapacitor 130 can maintain the DC link voltage converted through therectifier 120 and can supply the voltage to the inverter 140.

The inverter 140 can switch a voltage applied to the working coil 12(150) and can allow high-frequency current to flow in the working coil12 (150). For example, the inverter 140 can drive a switching deviceincluding an insulated gate bipolar transistor (IGBT) and can allowhigh-frequency current to flow in the working coil 12 (150), and thus, ahigh-frequency magnetic field can be formed in the working coil 12(150).

Current may or may not flow in the working coil 12 (150) according towhether the switching device is driven. For example, when current flowsin the working coil 12 (150), a magnetic field can be generated. Ascurrent flows in the working coil 12 (150), a magnetic field can begenerated to heat a cooking container.

As such, in the electromagnetic induction heating mode, the wirelesspower transmission apparatus 10 can heat the cooking container using theworking coil 12 (150) in electromagnetic induction.

When the wireless power transmission apparatus 10 functions in awireless power transmission mode, the working coil 12 (150) used ininductive heating can be used in wireless power transfer (WPT) in thesame way.

Wireless power transfer (WPT) refers to technology of transmitting powerwithout wire. A method used in wireless power transfer (WPT) can includea magnetic induction (MI) method or a magnetic resonance (MR) method.The magnetic induction (MI) method can use a magnetic inductionphenomenon between a primary coil and a secondary coil. For example,when current is injected into a primary (transmission) coil, a magneticfield can be generated. Induced current can be generated in thesecondary (reception) coil by the magnetic field generated in theprimary coil. The induced current generated in the secondary coil cancharge a battery. The magnetic field generated using a magneticinduction method may be weak, and thus, the primary coil and thesecondary coil need to be positioned adjacent to each other in order tocharge the battery.

The magnetic resonance (MR) method is a method in which primary andsecondary coils transmit and receive power using the same frequency. Forexample, when a magnetic field that oscillates at a resonance frequencyis generated in the primary coil, the secondary coil can be designed atthe same resonance frequency as the magnetic field generated in theprimary coil and can receive energy. In some implementations, it can bepossible to charge the battery at a relatively long distance.

As such, a corresponding function can be selectively performed accordingto user mode selection using the same structure by using a coil used inwireless power transfer (WPT) as the working coil 12 used in theinduction heating mode.

Referring back to FIG. 3, one side of the working coil 12 (150) can beconnected to a node of a switching device of the inverter 140, and theother side of the working coil 12 (150) can be connected to theresonance capacitor 160. The switching device can be driven by acontroller 190 (see FIG. 4) and can be controlled according to aswitching time output from the controller 190, and as the switchingdevice is alternately operated, a high-frequency voltage can be appliedto the working coil 12 (150). An on/off time of the switching deviceapplied from the controller 190 can be controlled to be graduallycompensated for, and thus, a voltage applied to the working coil 12(150) can be changed to a high voltage from a low voltage.

The controller 190 can control an overall operation of the wirelesspower transmission apparatus 10. For example, the controller 190 cancontrol each component included in the wireless power transmissionapparatus 10. The resonance capacitor 160 can be a component thatfunctions as a buffer. The resonance capacitor 160 can adjust asaturation voltage increase rate while the switching device is turnedoff and can affect energy loss during a turn-off time. The resonancecapacitor 160 can include a plurality of capacitors 160 a and 160 b thatare connected in series to each other between the working coil 12 (150)and the DC opposite ends to which a voltage from the rectifier 120 isoutput. The resonance capacitor 160 can include a first resonancecapacitor 160 a and a second resonance capacitor 160 b. For example, afirst end of the first resonance capacitor 160 a can be connected to afirst end to which a voltage from the rectifier 120 is output, and asecond end can be connected to a node of the working coil 12 (150) andthe second resonance capacitor 160 b. Similarly, a first end of thesecond resonance capacitor 160 b can be connected to the second end towhich a low voltage is output from the rectifier 120, and a second endcan be connected to the node of the working coil 12 (150) and the firstresonance capacitor 160 a.

Capacitance of the first resonance capacitor 160 a can be the same ascapacitance of the second resonance capacitor 160 b.

Depending on capacitance of the resonance capacitor 160, a resonancefrequency of the wireless power transmission apparatus 10 can bedetermined.

For example, the resonance frequency of the wireless power transmissionapparatus 10 configured as the circuit diagram shown in FIG. 3 can bedetermined depending on inductance of the working coil 12 (150) andcapacitance of the resonance capacitor 160. A resonance curve can beformed based on the resonance frequency determined depending on theinductance of the working coil 12 (150) and the capacitance of theresonance capacitor 160. The resonance curve can represent output powerdepending on a frequency.

A quality (Q) factor can be determined depending on an inductance valueof the working coil 12(150) included in the multi-functional wirelesspower transmission apparatus 10 and a capacitance value of the resonancecapacitor 160. The resonance curve can be differently formed dependingon the Q factor. A frequency at which maximum power is output can referto a resonance frequency (f0), and the wireless power transmissionapparatus can use a frequency of a right region based on the resonancefrequency (f0) of the resonance curve. Thus, the wireless powertransmission apparatus 10 can reduce a frequency to lower a firepowerstage and can increase the frequency to increase the firepower stage.The wireless power transmission apparatus 10 can adjust such a frequencyand can adjust output power. The wireless power transmission apparatus10 can use a frequency corresponding to a range to a second frequencyfrom a first frequency. For example, the wireless power transmissionapparatus can change a current frequency to any one frequency includedin the range to the second frequency from the first frequency and canadjust firepower. The first frequency as a minimum frequency and thesecond frequency as a maximum frequency that are to be controlled by thewireless power transmission apparatus 10 can be preset. For example, thefirst frequency can be 20 kHz and the second frequency can be 75 kHz.

As the first frequency is set as 20 kHz, the wireless power transmissionapparatus 10 can limit the case in which an audible frequency (about 16Hz to 20 kHz) is used. Thus, noise of the wireless power transmissionapparatus 10 cab be reduced. In some implementations, the secondfrequency can be set to an IGBT maximum switching frequency. The IGBTmaximum switching frequency can refer to a maximum frequency for drivingin consideration of internal pressure, capacitance, and the like of theIGBT switching device. For example, the IGBT maximum switching frequencycan be 75 kHz.

As such, a frequency that is generally used to heat a cooking took byinduction heating in the wireless power transmission apparatus 10 can bebetween 20 kHz to 75 kHz.

A frequency used in wireless power transfer (WPT) can be different froma frequency used for induction heating the cooking container by thewireless power transmission apparatus 10. For example, the frequencyused in wireless power transfer (WPT) can be a frequency with a higherband than a frequency used to heat a cooking container by the wirelesspower transmission apparatus.

Thus, the wireless power transmission apparatus can provide both acooking tool heating function and a wireless power transfer (WPT)function through the same working coil 12 (150) by adjusting a resonancefrequency.

FIG. 4 is an example of a circuit diagram of the case in which awireless power transmission apparatus is operated in a wireless powertransmission mode.

FIG. 4 shows an example of the wireless power transmission apparatus 10that selectively provides a cooking container induction heating mode anda wireless power transmission mode.

The wireless power transmission apparatus 10 can include the rectifier120, the DC link capacitor 130, the inverter 140, the working coil 12(150), the resonance capacitors 160 a and 160 b, WPT capacitors 170 aand 170 b, and mode conversion switches 180 a and 180 b.

The same description as the description given with reference to FIG. 3is omitted here.

The working coil 12 (150) can generate a magnetic field as current flowstherein. In some implementations, the magnetic field generated in theworking coil 12 (150) can heat the target object 1 of a secondary sideas being transmitted through the cooking container of the secondaryside.

In some implementations, the magnetic field generated by the workingcoil 12 (150) can transmit power to a small home appliance of thesecondary side as being transmitted through the small home appliance ofthe secondary side.

The resonance capacitors 160 a and 160 b can be the same as in thedescription given with reference to FIG. 3. That is, the resonancecapacitors 160 a and 160 b shown in FIG. 4 can be the same as theresonance capacitor included in the wireless power transmissionapparatus 10 as described above with reference to FIG. 3.

As the wireless power transmission apparatus 10 is operated in awireless power transmission mode or a cooking container inductionheating mode, the resonance capacitors 160 a and 160 b may or may not beconnected in parallel to the WPT capacitors 170 a and 170 b.

In some implementations, the WPT capacitors 170 a and 170 b can beconnected in parallel to the resonance capacitors 160 a and 160 b. TheWPT capacitors 170 a and 170 b can be a component for lowering aresonance frequency of the wireless power transfer (WPT) to operate anelectromagnetic induction heating cooking device 100 in the wirelesspower transmission mode. For example, when the wireless powertransmission apparatus 10 is operated in the cooking container inductionheating mode, the WPT capacitors 170 a and 170 b may not be connected tothe resonance capacitors 160 a and 160 b. By way of further example,when the wireless power transmission apparatus 10 is operated in thewireless power transmission mode, the WPT capacitors 170 a and 170 b canbe connected in parallel to the resonance capacitors 160 a and 160 b.When the WPT capacitors 170 a and 170 b are connected in parallel to theresonance capacitors 160 a and 160 b, composite capacitance canincrease. When the composite capacitance increases, the resonancefrequency (f0) can be reduced according to Equation 1 below.

For example, when the electromagnetic induction heating cooking device100 is operated in the wireless power transmission mode, the resonancefrequency (f0) can be reduced. As such, the wireless power transmissionapparatus 10 can reduce the resonance frequency (f0) and can wirelesslytransmit power to a product of a secondary side using the originalinverter 140 and working coil 12 (150).

The WPT capacitors 170 a and 170 b can include the first WPT capacitor170 a and the second WPT capacitor 170 b. In some implementations, thefirst WPT capacitor 170 a can be connected in parallel to the firstresonance capacitor 160 a, and the second WPT capacitor 170 b can beconnected in parallel to the second resonance capacitor 160 b.

Capacitance of the first WPT capacitor 170 a can be the same ascapacitance of the second WPT capacitor 170 b.

The mode conversion switches 180 a and 180 b can determine whether theWPT capacitors 170 a and 170 b and the resonance capacitors 160 a and160 b are connected in parallel to each other. For example, the modeconversion switches 180 a and 180 b can perform control to connect ornot connect the WPT capacitors 170 a and 170 b in parallel to theresonance capacitors 160 a and 160 b.

For example, when the mode conversion switches 180 a and 180 b areturned on, a circuit can be shorted, and the WPT capacitors 170 a and170 b and the resonance capacitors 160 a and 160 b can be connected inparallel to each other. Thus, as described above, the resonancefrequency (f0) can be reduced.

In some implementations, when the mode conversion switches 180 a and 180b are turned off, the circuit can be open, and the WPT capacitors 170 aand 170 b may not be connected to the resonance capacitors 160 a and 160b. Thus, the resonance frequency (f0) may not be changed.

The mode conversion switches 180 a and 180 b can include the first modeconversion switch 180 a and the second mode conversion switch 180 b, andthe first mode conversion switch 180 a and the second mode conversionswitch 180 b can be simultaneously operated. The first mode conversionswitch 180 a can determine whether the first WPT capacitor 170 a and thefirst resonance capacitor 160 a are connected in parallel to each other,and the second mode conversion switch 180 b can determine whether thesecond WPT capacitor 170 b and the second resonance capacitor 160 b areconnected in parallel to each other.

In some implementations, the mode conversion switches 180 a and 180 bcan be controlled depending on an operation mode, and can be operated inthe wireless power transmission mode or the induction heating modethrough the same working coil 12 (150).

For example, one mode of the two modes can be selectively operatedthrough a user input unit according to user selection.

The wireless power transmission apparatus 10 can further include thecontroller 190 for controlling on and off of the conversion switches 180a and 180 b depending on such mode selection, controlling on and off aswitching device of the inverter 140, and controlling an overalloperation of a driving module.

In some implementations, when the induction heating mode is selectedusing a user input unit, the controller 190 of the wireless powertransmission apparatus 10 can be operated in the induction heating mode,and the conversion switches 180 a and 180 b can be turned off to performinduction heating.

In some implementations, when the wireless power transmission mode ofthe target object 1 is selected using the user input unit, the wirelesspower transmission apparatus 10 can be operated in the wireless powertransmission mode, the conversion switches 180 a and 180 b can be turnedon, and wireless power transfer (WPT) can be performed at a resonancefrequency based on composite capacitance.

In some implementations, the wireless power transmission apparatus 10needs to perform whether the target object 1 positioned on the upperglass 11 is capable of wirelessly transmitting power.

Even if a user selects the wireless power transmission mode through theuser input unit, when the target object 1 positioned on the wirelesspower transmission apparatus is an electronic product that is notcapable of performing wireless power transfer (WPT) or a small homeappliance having no reception coil but not a small home appliance havinga reception coil, the wireless power transmission apparatus 10 candifferently perform the operation.

When the operation is performed based on only mode selection informationreceived through the user input unit, overcurrent may flow in the targetobject 1 having no reception coil, or in the case of a foreign object, awaste of electricity may also be caused due to overcurrent and high heatmay be accompanied, and thus, the apparatus may be damaged.

When the target object 1 is a small home appliance having the receptioncoil 15, an alignment state between the reception coil 15 and theworking coil 12 may need to be determined.

When the reception coil 15 and the working coil 12 are not aligned witheach other, that is, in the case of eccentricity, an operation frequencyof wireless power transmission needs to be controlled to perform powertransmission for which eccentricity is compensated.

In some implementations, a configuration of a reception side, that is, atarget object can be, for example, the same as in FIG. 5, and analignment state between the reception coil and the working coil of thetarget object can be shown in FIG. 6.

FIG. 5 is a diagram illustrating a configuration of a target object at areception side. FIG. 6 is a state diagram illustrating an alignmentstate between a reception coil and a working coil.

Referring to FIG. 5, the target object 1, which can be a small homeappliance having the reception coil 15, can include the reception coil15, a reception power processor 21 connected to the reception coil 15and configured to process received wireless power, a small appliancecontroller 25, an internal load 23, and a communicator 24.

For the small home appliance having the reception coil 15, the receptioncoil 15 can be disposed on a bottom surface or the like, can be formedto face the working coil 12, and can be configured to wirelessly receivepower.

The small home appliance having the reception coil 15 can be a smallhome appliance including the internal load 23 as a functional block,such as a wireless oven toaster or a wireless blender, and can includethe reception power processor 21 for wirelessly receiving power,converting corresponding power to a desired level, and providing thepower to the internal load 23 with a desired function.

The reception power processor 21 can include a converter for rectifyingcurrent and voltage in the reception coil 15 and converting therectified current and voltage to a desired level.

The communicator 24 can wirelessly communicate with the wireless powertransmission apparatus 10 for induction heating, can transmitinformation regarding a load voltage, target output of the small homeappliance, or the like, and can also transmit information regardingwhether the internal load 23 is driven.

The small home appliance having the reception coil 15 can include thesmall appliance controller 25 for controlling the reception powerprocessor 21, the internal load 23, and the communicator 24, and thesmall appliance controller 25 can control each functional blockaccording to a command from an external user, that is, a command througha user interface or the like, and can supply power required by theinternal load 23 to drive the internal load 23.

Thus, it can be possible to wirelessly supply power and to perform adesired function, and thus, power can be supplied from the wirelesspower transmission apparatus 10 without power supply by wire, theinternal load 23 can be driven, and a function of a toaster, a blender,or the like can be performed.

When the small home appliance having the reception coil 15 is positionedon the upper glass 11, alignment between the reception coil 15 and theworking coil 12 can proceed.

Alignment between the reception coil 15 and the working coil 12 can bedefined based on whether the centers of the two coils 12 and 15 arepositioned on the same axis.

For example, as schematically shown in FIG. 6, assuming that the centralpoints n1 and n2 of the respective coils, that is, the central point n2of the reception coil 15 and the central point n1 of the working coil 12are positioned on the single plane, an eccentricity amount dl can bedefined as a straight distance between the two central points.

In some implementations, for wireless power transfer of a small homeappliance having the reception coil 15, for example, a blender or anoven toaster, the reception coil 15 needs to be aligned with the workingcoil 12 at a short distance that satisfies a predetermined distance.

Alignment can be defined as constancy, that is, a state in which the twocentral points n1 and n2 are homocentric on the single plane assumingthat the two coils 12 and 15 are positioned on the single plane P1, thatis, a state in which the central point n2 of the reception coil 15 andthe central point n1 of the working coil 12 are homocentric on an axisperpendicular to an imaginary single plane P1.

Eccentricity corresponds to the case in which central points n1 and n3of the two coils 12 and 15 are not homocentric on the axis perpendicularto the imaginary single plane P1, and as shown in FIG. 6, a distance dlbetween the two central points n2 and n3 on the imaginary single planeP1 can be defined as an eccentricity degree.

Thus, the eccentricity degree can be defined as the straight distance dlon the imaginary single plane and may not be a diagonal distance ondifference planes.

In some implementations, in order to smoothly perform wireless powertransfer between the two coils 12 and 15, the eccentricity degree needsto be a predetermined range or less, and as the eccentricity degree isincreased, transmission efficiency of wireless power transfer may belowered, and to detect this, an error may occur in a detection signal.

Thus, when such an error occurs, the accuracy of detecting a foreignobject or the like may be remarkably degraded, thereby degradingreliability in an operation.

Thus, the present disclosure proposes a method of determining aneccentricity degree, compensating for this, detecting whether a foreignobject is present, and wirelessly transmitting power during wirelesspower transfer.

Hereinafter, the whole operation of a wireless power transmissionapparatus for induction heating will be described with reference toFIGS. 7 and 8.

FIG. 7 is a schematic flowchart illustrating an exemplary process for amode of a wireless power transmission apparatus for induction heatingaccording to an embodiment of the present invention. FIG. 8 is a diagramillustrating a structure of a transmission apparatus and a receptionapparatus with respect to the flowchart of FIG. 7.

Referring to FIGS. 7 and 8, when the controller 190 receives selectioninformation corresponding to selection of an icon or a button of awireless power transmission mode by selecting the icon or the buttonfrom a user input unit, the wireless power transmission apparatus forinduction heating can be converted into the wireless power transmissionmode and can perform an operation.

The wireless power transmission apparatus 10 for induction heating canhave a preparation period through a plurality of operations to a normaloperation mode S60, that is, an operation of wirelessly emitting powertowards the reception target object 1.

The wireless power transmission apparatus 10 for induction heating canperform detection for identifying the target object 1 positioned on theupper glass 11 in the preparation period prior to the normal operationmode.

For example, the target object 1 can be identified by determiningwhether the target object 1 is (i) a small home appliance having areception coil, (ii) a small home appliance that is directly heatedwithout a reception coil and has only a pick up coil, (iii) a generalheating container, (iv) a foreign object, or (v) in a no-load state inwhich there is nothing.

For example, when receiving mode selection information (S10), thewireless power transmission apparatus 10 can enter a target objectdetection mode S20 in terms of a transmission side.

The wireless power transmission apparatus 10 defined as the transmissionside can execute a foreign object detection mode S40 and a soft startmode S50 through a target object detection mode S20 and a stand-by modeS30.

In the soft start mode S50, prior to entry into the normal operationmode S60, detection of all the target objects 1 can be terminated andcorresponding power can be wirelessly transmitted (S70).

The target object detection mode S20 can be simultaneously executed whena user pushes a wireless power transmission mode icon or button of auser input unit, and the controller 190 can oscillate frequencies fordetermining whether the target object 1 is positioned on the upper glass11 and predicting an alignment state.

In some implementations, a switching device of the inverter 140 can bealternately turned on and off to allow current to flow according to theoscillation frequency. Whether the target object 1 identified in thetarget object detection mode S20 is a general heating container can bedetermined whether the target object 1 is a heating container can bedetermined while switching to a first operation frequency from a startfrequency.

In the target object detection mode S20, whether the target object 1 ispresent and whether the target object 1 has a coil can be determined,and when the coil is present, whether the reception coil 15 and theworking coil 12 of the target object 1 are aligned with each other, thatis, whether the coils are positioned in constancy or eccentricity can beadditionally determined.

In the target object detection mode S20, the wireless power transmissionapparatus 10 can attempt wireless communication with the target object1, and reception through wireless communication can be started bycommunication pairing when power of a small home appliance that is thetarget object 1 is supplied in the foreign object detection mode.

An idle mode can be defined as a start mode in which the controller 190is activated by supplying power to a driving module including thecontroller 190 of the wireless power transmission apparatus 10 forinduction heating when a user pushes and turns on a power button througha user input unit.

In the idle mode, wired communication between the user input unit andthe driving module can be performed.

The stand-by mode S30 can be an operation after the target objectdetection mode S20, and can be defined as a frequency change period inwhich the inverter 140 is driven at a second operation frequency inorder to determine a foreign object when the target object 1 is presentin a region for wireless power transfer.

In some implementations, in the stand-by mode S30, frequency sweep canoccur from an initial operation frequency to a second operationfrequency, and when the second operation frequency is reached, a currentmode can substantially enter the foreign object detection mode S40.

In some implementations, the second operation frequency may notoscillate from the beginning because oscillation needs to besequentially induced since driving noise is generated when the apparatusis driven at the second operation frequency, that is, a lower frequencythan the initial operation frequency in a state in which a voltage of aDC link is charged.

The foreign object detection mode S40 can be defined as a period inwhich load voltage information of the target object is received andwhether a foreign object is present in a state in which the apparatus isdriven at the second operation frequency and communication pairing witha reception side, that is, the target object 1 is performed.

In some implementations, when the foreign object is determined to bepresent, the apparatus can enter the idle mode again and informationindicating that the foreign object is present can be signaled to a user,and when there is no foreign object, the apparatus can enter the softstart mode S50.

For example, a state that is activated by injecting power into thereception side, that is, the target object 1 due to induced current fromthe foreign object detection mode S40 can be defined as a wakeup mode,and in this case, wireless communication is paired between the receptionside and the transmission side and communication can begin therebetween.

The soft start mode S50 can be defined as a period in which power of alevel requested by the target object 1 is changed to a frequencycorresponding to corresponding power for an operation in the wirelesspower transmission apparatus 10.

When the power of the level requested by the target object 1 isapproximately reached in the soft start mode S50, a current mode canenter the normal operation mode S60.

In the soft start mode S50, an additional detection mode can beexecuted.

The additional detection mode can be defined as a period in whichadditional detection is performed for recheck prior to power transfer ofa small home appliance.

For example, in the additional detection mode, a mode that is actuallyselected by a user can be rechecked, and whether there is an error ofjudgment between no load and a small home appliance can be rechecked.

The normal operation mode S60 can be defined as a period in which changein requested output is monitored and whether there is a differencebetween actual output and the requested output is determined with aconstant level at power of the level requested by the target object 1.

In some implementations, when there is the difference between the actualoutput and the requested output, if the actual output is lower than therequested output, a power up mode can proceed to lower an operationfrequency and to increase output, and if the actual output is higherthan the requested output, a power down mode can proceed to increase theoperation frequency and to lower the output.

At a side of the target object 1, according to user operation selectionand operation time of the target object 1 or according to request forlow power or high power, the controller 190 can perform an operationusing requested output based on the request.

As such, in some implementations, as the foreign object detection modeS40 is executed, a parameter for other situations such as eccentricitycan be removed and then a foreign object can be detected (S40).

For example, in the foreign object detection mode S40, when a loadvoltage can be received from the target object 1 and a foreign object ispresent, wireless power transmission efficiency may be degraded, andthus, reduction in a load voltage can be detected to determine whether aforeign object is present.

Under a condition in which an input voltage of a wireless powertransmission apparatus is changed, or when eccentricity occurs between atarget object and a working coil, reduction in the load voltage may alsooccur.

Thus, the present disclosure provides a method of compensating for andremoving parameters related to the case in which an input voltage ischanged or eccentricity occurs, and determining whether a foreign objectis present.

Hereinafter, a method of detecting a foreign object in a foreigndetection mode will be described in detail with reference to FIGS. 9 to11C.

FIG. 9 is a flowchart illustrating an exemplary operation of determiningeccentricity and a foreign object during power transfer. FIGS. 10A and10B are graphs illustrating a compensating method depending on an inputvoltage. FIGS. 11A, 11B, and 11C illustrating graphs showing an exampleof eccentricity compensation.

Referring to FIG. 9, when a stand-by mode is terminated and a foreignobject detection mode begins, wireless power transfer can begin whiledriving the inverter 140 at the second operation frequency andperforming communication with the target object 1 (S100).

In some implementations, wirelessly transmitted power can refer to asmall amount of power in a preparation operation but not power thatreaches desired output.

Thus, in the inverter 140 of the wireless power transmission apparatus10 for induction heating, a switching device can be turned on or off bya second operation frequency to allow input current to flow, and thus, astandby voltage can be set in the working coil 12 to allow resonancecurrent to flow.

In some implementations, the controller 190 can receive informationregarding a load voltage through wireless communication from thecommunicator 24 of a small home appliance that if the target object 1(S110).

The controller 190 can read a corresponding load voltage and cancompensate for a corresponding load voltage value depending on a currentinput voltage.

For example, when the current input voltage is not a first referenceinput voltage, the controller 190 can compensate for the amplitude ofthe received load voltage by the first reference input voltage and cancalculate the compensated load voltage.

Such switch of load voltage can be performed through the followingtable.

TABLE 1 After compensation Prior to input voltage compensation LoadInput Resonance Input Resonance Load Load voltage Input current currentLoad current current Voltage voltage actual voltage (44 kHz) (44 kHz)voltage deviation deviation deviation compensation value 193 372 452 7134 253 79 150 152 193 372 452 71 34 253 79 150 193 372 450 71 34 255 79150 193 372 452 71 34 253 79 150 204 377 493 84 29 212 66 150 151 204376 493 84 30 212 66 150 204 376 493 84 30 212 66 150 204 377 493 84 29212 66 150 214 383 533 96 23 172 54 150 150 214 383 533 96 23 172 54 150214 382 534 96 24 171 54 150 214 383 534 96 23 171 54 150 226 392 581111 14 124 39 150 151 226 392 581 111 14 124 39 150 226 391 582 111 15123 39 150 226 390 582 111 12 123 39 150 237 395 624 124 11 81 26 150151 237 395 624 124 11 81 26 150 237 395 624 124 11 81 26 150 237 395623 124 11 82 26 150 248 401 666 137 5 39 13 150 151 248 401 666 137 539 13 150 248 401 666 137 5 39 13 150 248 401 666 137 5 39 13 150 259406 705 150 0 0 0 150 151 259 407 708 150 −1 −3 0 150 259 406 706 150 0−1 0 150 259 406 706 150 0 −1 0 150

For example, as shown in Table 1 above, the controller 190 can havereference data of a value of input current and a value of resonancecurrent at a second operation frequency and a value of a load voltage ofthe target object 1 depending on a value of an input voltage, that is, avalue of an input voltage that is commercially available power providedto the wireless power transmission apparatus 10 from a wall powersource.

The type and size of a small home appliance that is the target object 1that wirelessly receives power through the corresponding wireless powertransmission apparatus 10 can be limited, and the amplitude of a loadvoltage that is already set in the reception coil 15 when the receptioncoil 15 is designed can be stored and retained as experimental datadepending on the amplitude of an operation frequency.

Thus, by receiving a load voltage of a specific input voltage withrespect to a second operation frequency in an actual operation, thecontroller 190 can compensate for the load voltage by a value of a firstreference input voltage.

In some implementations, the first reference input voltage can be 259 V.In some implementations, the first reference input voltage can be avalue other than 259V.

Table 1 is based on the case in which the first operation frequency is44 kHz. For example, the first operation frequency can be a differentvalue other than 44 kHz.

The controller 190 can calculate graphs shown in FIGS. 10A and 10B basedon a value of input current supplied to the inverter 140 when theinverter 140 is driven at a second operation frequency with respect toan input voltage with various amplitudes, and information regarding avalue of resonance current flowing in the working coil 12 and a loadvoltage applied to the reception coil 15 of the target object 1, whichis a reception end for wirelessly receiving power.

In some implementations, the controller 190 can calculate resonancecurrent and input current when the first reference input voltage is 259V, resonance current at a different input voltage from a load voltage,and a deviation of input current and a load voltage at a secondoperation frequency as shown in Table 1 above.

In some implementations, the resonance current and the input current canbe a predetermined integrated value of values detected every count.

For example, such a calculation result can be shown in a right side ofTable 1.

By way of further example, such deviation information can be retained inthe controller 190.

The controller 190 can calculate graphs illustrated in FIGS. 10A and 10Bwith respect to resonance current, input current, and a load voltage.

In each graph, the x axis indicates an input voltage and the y axisindicates a deviation value of each parameter.

For example, FIG. 10A relates to resonance current and is a graphillustrating a resonance current deviation (a difference betweenresonance current at the first reference input voltage and resonancecurrent at a corresponding input voltage) with respect to an inputvoltage.

Referring to FIG. 10A, the corresponding graph can be derived as a firstorder function f1, and thus, it can be possible to calculate aninclination and a y intercept.

FIG. 10C relates to a load voltage and is a graph showing a load voltagedeviation (a difference between a load voltage at a first referenceinput voltage and a load voltage at a corresponding input voltage) withrespect to an input voltage.

Referring to FIG. 10B, the corresponding graph can also be derived as afirst order function f2, and thus, it can be possible to calculate aninclination and a y intercept.

It can also be possible to calculate a function of input current asillustrated in FIG. 10A or 10B.

Thus, when a current input voltage value is known from each function andload voltage information is read based on information from the targetobject 1, this can be applied to the function based on each graph tocalculate a deviation value.

Thus, a corresponding deviation value can be added to a current loadvoltage value, and thus, a load voltage value recalculated based on afirst reference input voltage but not the current input voltage can becalculated as a compensated load voltage value.

In the same method, the controller 190 can calculate correspondingresonance current and an input current value as compensated resonancecurrent and compensated input current that are recalculated when thefirst reference input voltage but not values with respect to the currentinput voltage.

In some implementations, the controller 190 can calculate a compensatedvalue of resonance current and input current with respect to the firstreference input voltage (S120) and can compensate for a load voltagewhen the compensated value of the resonance current is greater than thecompensated input current (S130).

For the compensation, when compensated resonance current is not greaterthan compensated input current, a foreign object can be determined to bepresent, and an operation can be terminated.

When the compensated value of the resonance current is greater than theinput current, the controller 190 can compensate for a load voltage ofthe target object 1 with respect to the first reference input voltageand can calculate the compensated load voltage value (S140).

In some implementations, the controller 190 can store functions of therespective graphs with respect to parameters, that is, resonancecurrent, input current, and load voltage, and can perform calculation ona value obtained digitizing and detecting an inclination and y interceptof each function.

In some implementations, a compensation equation of each parameter canbe modified as follows.

For example, in FIG. 10A, a graph of an analog value with respect toresonance current can be represented according to the following functionf1.

y=−0.8851x+1003.1  [Equation 1]

As described above, x is an input voltage, and y is a deviation in anintegrated value of resonance current (a difference of an integratedvalue of resonance current in a current input voltage with respect to afirst reference input voltage). In some implementations, when a value ofresonance current is large, it can be possible to replace a value ofresonance current in a specific count but not an integrated value of aplurality of counts.

Equation 1 above can be digitized to Equation 2 below and can becalculated by the controller 190.

Compensated resonance current=current resonance current integratedvalue+second compensated value−first compensated value, where

First compensated value=3*current input voltage+600*current inputvoltage/2¹⁰, and

Second compensated value=k  [Equation 2]

For example, the current resonance current integrated value can be anintegrated value of resonance current with respect to a predeterminedcount, and the current input voltage can be an RMS voltage value ofcurrent wall power, that is, commercially available power.

In some implementations, the second compensated value can be variedaccording to a function value, but can be set to 935 with respect toEquation 1 above with respect to a current graph.

Similarly, it can be possible to convert a value of input current.

For example, it can be calculate an analog function using data of aninput current integrated value, and calculation of digitizing acorresponding analog function value can be performed.

In some implementations, calculation for digitization can be performedaccording to Equation 3 below.

Compensated input current=current input current integrated value+secondcompensated value−first compensated value, where

First compensated value=543*current input voltage/2¹⁰, and

Second compensated value=m  [Equation 3]

For example, m can be determined depending on a function value but maybe 137 with respect to Table 1 above.

By way of further example, a value of a load voltage can also becalculated in a similar way.

In some implementations, a function calculated based on FIG. 10B cansatisfy Equation 4 below.

y=−1.2007x+310.76  [Equation 4]

In some implementations, as described above, x can be an input voltage,and y can be a deviation in a load voltage value (a difference of a loadvoltage between a load voltage in a first reference input voltage and aload voltage in a current input voltage).

Equation 4 above can be digitized to Equation 5 below and can becalculated by the controller 190.

Compensated load voltage=current load voltage+second compensatedvalue−first compensated value, where

First compensated value=current input voltage+300*current inputvoltage/2¹⁰, and

Second compensated value=n  [Equation 5]

For example, the second compensated value can be varied depending on afunction value but may be set to 332 with respect to Equation 4 abovewith respect to a current graph.

As such, the received value can be digitized and can be inserted intoeach function to acquire a deviation in parameters, and the deviationcan be added to a current data value to calculate a compensated loadvoltage with respect to the first input reference voltage.

Thus, even if the input voltage is not the first input reference value,the controller 190 can recalculate the load voltage and can perform thefollowing calculation in the case of the first input reference voltage.

Whether a foreign object is present can be determined with respect tothe load voltage that is recalculated and compensated for, and thus, anaccurate voltage variation may due to a foreign object be detectedwithout consideration of transition of the load voltage with respect toa variation in the input voltage.

Then, the controller 190 can compensate for reduction in a load voltagedue to eccentricity between the working coil 12 and the reception coil15 of the target object 1 (S150).

For example, voltage reduction due to eccentricity that occurs betweenthe two coils 12 and 15 can be compensated for, and thus, a factor forvoltage reduction can be limited only to a foreign object, and whether aforeign object is present can be accurately determined according to thecompensation result.

Compensation in the load voltage due to eccentricity can be calculatedaccording to Table 2 below.

TABLE 2 Prior to eccentricity compensation Load Eccentricity InputResonance Load voltage degree current current voltage deviation 0 384603 187 −35 0 385 603 187 −35 0 382 603 187 −35 0 382 603 187 −35 10 386627 182 −30 10 387 627 182 −30 10 387 627 182 −30 10 387 627 183 −31 15392 645 177 −25 15 392 645 177 −25 15 392 645 176 −24 15 392 645 176 −2420 401 671 166 −14 20 401 671 166 −14 20 399 671 164 −12 20 399 671 164−12 25 407 704 152 0 25 407 704 152 0 25 406 704 152 0 25 407 704 152 0

Referring to Table 2 above, the controller 190 can retain data aboutinput current, resonance current, and a load voltage of an eccentricitydegree at a second operation frequency in the case of a first referenceinput voltage.

For example, the data of Table 2 above can be a value of each parametercalculated via an experiment or a simulation, and the controller 190 canstore and retain data about an eccentricity degree of each parameterwith respect to a second reference input voltage to be described lateras well as the first reference input voltage.

The controller 190 can calculate a deviation value of a firsteccentricity degree with respect to data of each parameter and can storethe calculated deviation value with Table 2 above.

In some implementations, the first eccentricity degree can be set to 25mm that is the maximum eccentricity degree.

An input current deviation, a resonance current deviation, and a loadcurrent deviation can each be calculated with respect to the firsteccentricity degree, and a graph of a deviation value of each parameterand an eccentricity degree can be obtained as shown in FIGS. 11A, 11B,and 11C.

For example, FIG. 11A is a graph illustrating a load voltage withrespect to various eccentricity degrees prior to eccentricitycompensation.

With respect to such values, as shown in FIG. 11B, when a graph isderived by deriving a deviation with respect to the first eccentricitydegree and then calculating the deviation value as the y and calculatingthe compensated resonance current (a compensated value with respect tothe first reference input voltage) as the x axis, a function f3 of acorresponding load voltage deviation can satisfy Equation 6 below.

y=0.3579x−253.17  [Equation 6]

For example, when Equation 6 is applied to assume that a load voltageformed by compensating for an input voltage has the first eccentricitydegree, a load voltage value obtained by compensating for a deviationcan have the same/similar level value with respect to all eccentricitydegrees as shown in FIG. 11C.

In some implementations, as described above, a function value withrespect to a load voltage can have an analog value, and thus, thefunction value can be digitized and can be calculated by the controller190 according to Equation 7 below.

Deviation compensated load voltage=input voltage compensated loadvoltage+first compensated value−second compensated value, where

First compensated value=367*resonance current integrated value/2¹⁰, and

Second compensated value=a  [Equation 7]

For example, the second compensated value can be varied depending on afunction value but may be set to 253 with respect to Equation 7 abovefor the current graph.

A deviation can be obtained by digitizing the received integrated valueof the resonance current and inserting the integrated value into aneccentricity compensation function f3 and can be added to a current datavalue, and thus, a first last load voltage can be calculated withrespect to compensation and deviation with respect to the first inputreference voltage.

The controller 190 can determine whether a foreign object is presentbased on the calculated first last load voltage (S160).

For example, when the first last load voltage value satisfies a firstvalue V1 or greater and satisfies a second value V2 or less, it can bedetermined that there is no foreign object (S200) and a current mode canenter a soft start mode that is a next operation.

When the first last load voltage does not satisfy a value between thefirst value V1 and the second value V2, the controller 190 canrecalculate compensation of a load voltage with respect to a secondreference input voltage (S170).

For example, the controller 190 can also store data shown in Table 1above with respect to the second reference input voltage and cancompensate for an integrated value of corresponding input current and anintegrated value of resonance current with respect to the secondreference input voltage (S160).

In some implementations, the second reference input voltage can satisfy220 V.

Thus, a deviation of each parameter in the case of the second referenceinput voltage can be calculated, and a function between the deviationfor each parameter and the input voltage can be derived.

When generating a function of each parameter, the controller 190 cancalculate the integrated value of resonance current and the integratedvalue of input current that are compensated for by digitizing such theequation.

In some implementations, the integrated value of input current that isdigitized and compensated can correspond to Equation 8 below, and thecompensated integrated value of the resonance current can correspond toEquation 9 below, and each coefficient can be changed according to afunction of a parameter.

Compensated integrated value of input current=integrated value ofcurrent input current+second compensated value−first compensated value,where

First compensated value=556*current input voltage/2¹⁰, and

Second compensated value=b  [Equation 8]

For example, b can be determined depending on a function value, and, insome implementations, can be 80.

Compensated resonance current integrated value=current resonance currentintegrated value+second compensated value−first compensated value, where

First compensated value=3*current input voltage+429*current inputvoltage/2¹⁰, and

Second compensated value=c  [Equation 9]

For example, the current integrated value of the current resonance canbe an integrated value of a detection value of resonance current withrespect to a predetermined count, and the current input voltage can bean RMS voltage value of current wall power, that is, commerciallyavailable power.

In some implementations, the second compensated value can be varieddepending on a function value. For example, the second compensated valuecan be 771.

As such, when the integrate value of the resonance current obtained bycompensating for the current input voltage value and the integratedvalue of input current are calculated with respect to the secondreference input voltage, the corresponding integrated value of inputcurrent and the integrated value of resonance current can be comparedwith each other (S170).

For example, when the compensated integrated value of resonance currentis smaller than the integrated value of input current, the controller190 can determine whether a foreign object is present.

In some implementations, when the compensated integrated value ofresonance current is greater than the integrated value of input current,the controller 190 can determine that wireless power transmission issmoothly performed, can compensate for a load voltage with respect tothe second reference input voltage, and can compensate for eccentricityin the corresponding value to calculate a second last load voltage(S180).

When such compensation of an input voltage and eccentricity based on thefirst reference input voltage with respect to the load voltage includesdata shown in the above Tables 1 and 2 with respect to the secondreference input voltage, the compensated value can be derived accordingto a function calculated based on corresponding data.

In some implementations, the corresponding function can be digitized andcalculated according to Equations 10 and 11 below.

Compensated load voltage=current load voltage+second compensatedvalue−first compensated value, where

First compensated value=current input voltage+322*current inputvoltage/2¹⁰, and

Second compensated value=d  [Equation 10]

For example, the second compensated value can be varied depending on afunction value. In some implementations, the second compensated valuecan be set to 297.

As such, the received value can be digitized and can be inserted intoeach function to acquire a deviation, and the deviation can be added toa current data value to calculate a compensated load voltage withrespect to the second input reference voltage.

The deviation can be compensated for by applying the compensated loadvoltage with respect to the second input reference voltage to Equation11 below.

Deviation compensated load voltage=input voltage compensated loadvoltage+first compensated value−second compensated value, where

First compensated value=330*resonance current integrated value/2¹⁰, and

Second compensated value=e  [Equation 11]

For example, the second compensated value can be varied depending on afunction value. In some implementations, the second compensated valuecan be set to 158.

As such, when the received value is digitized and a load voltagedeviation for compensating for eccentricity is added to the compensatedload voltage with respect to the second reference input voltage, thecompensated second last load voltage can be calculated with respect tothe compensation and deviation for the second input reference voltage.

The controller 190 can determine whether a foreign object is presentbased on the calculated second last load voltage (S190).

For example, when the second last load voltage value satisfies a thirdvalue V3 or greater and satisfies a fourth value V4 or less, it can bedetermined that a foreign object is not present and a current mode canenter a soft start mode that is a next operation.

When the second last load voltage does not satisfy a value between thethird value V3 and the fourth value V4, the controller 190 can determinethat a foreign object is present.

In some implementations, the first value V1 and the second value V2 thatare a threshold value of the first last load voltage can be the same asthe third value V3 and the fourth value V4, respectively, but can bedifferent from each other in such a way that the values indicatedifferent ranges. For example, only some of the threshold values can bedifferent. By way of further example, the first to fourth V1 to V4values can be 149, 200, 138, and 200, respectively.

As such, when the input voltage with respect to the first referenceinput voltage can be compensated for, and whether a foreign object ispresent can be primarily determined. If the foreign object is determinedto be present, the same calculation can be performed on the secondreference input voltage again, and if the foreign object is determinedto be present with respect to the second reference input voltage, theforeign object can be determined to be present.

When determining that a foreign object is present, the controller 190can stop transmitting power, that is, can stop driving the inverter 140,can provide an alarm to a user, and can guide removal of the foreignobject (S200).

As such, in order to determine reduction in a load voltage due to aforeign object, whether a foreign object is present can be obviouslydetermined by performing compensation for removing all other factors ofvoltage reduction and performing calculating a plurality of numbers oftimes to ensure reliability in determination.

Thus, whether a foreign object is present can be obviously determined,and when the foreign object is present, an operation can be stopped andthe foreign object can be removed via a user alarm, and thus, wirelesspower transfer can be safely performed.

Through the above solution, the multi-functional wireless powertransmission device using one working coil can determine whethereccentricity occurs in a target object, can compensate for this, and canperform wireless power transfer (WPT) in the wireless power transmissionmode while selectively driving the wireless power transmission mode orthe induction heating mode.

As such, the present disclosure can provide a wireless powertransmission apparatus for providing an alarm to a user during wirelesspower transfer when a wireless power transmission mode is selected, if atarget object is a small home appliance having a reception coil andexcessive eccentricity occurs between the corresponding reception coiland a working coil of a transmission side. In some implementations,whether a foreign object is present as well as whether eccentricityoccurs can be determined, and thus, a user alarm can also be provided.

In addition, a difference in an input voltage and an eccentricity degreecan be compensated for and a foreign object can be detected, and thus,the foreign object can be detected irrespective of the amplitude of theinput voltage and the eccentricity degree, thereby ensuring reliabilityand operation stability.

What is claimed is:
 1. A wireless power transmission apparatus forinduction heating comprising: a working coil configured to changeoperation based on selection of a mode of operation from among aplurality of operating modes, the plurality of operating modes includinga wireless power transmission mode configured to wirelessly transmitpower and a heating mode configured to heat one or more objects; aninverter configured to output, to the working coil, current at anoperation frequency; and a controller configured to: receive, in thewireless power transmission mode, a load voltage from a target object,compensate for the load voltage, and determine, in the wireless powertransmission mode, whether a foreign object is present in the workingcoil based on the compensated load voltage.
 2. The wireless powertransmission apparatus of claim 1, wherein the controller operates in apreparation period prior to a normal wireless power transmission modeconfigured to perform wireless power transmission to the target object,and wherein the controller is configured to determine, in thepreparation period, whether the foreign object is present in the workingcoil.
 3. The wireless power transmission apparatus of claim 2, whereinreceiving the load voltage from the target object includes receivinginformation regarding the load voltage from the target object, andwherein compensating for the load voltage includes compensating for theload voltage based on a current input voltage.
 4. The wireless powertransmission apparatus of claim 3, wherein the controller is configuredto: recalculate the current input voltage based on a first referenceinput voltage, perform compensation for removing variation in the loadvoltage with respect to the current input voltage, and calculate thecompensated load voltage.
 5. The wireless power transmission apparatusof claim 4, wherein the controller is configured to (i) compensate foran eccentricity degree between the working coil and a reception coil ofthe target object with respect to the calculated compensated loadvoltage and (ii) calculate a first calculated load voltage based on thecompensation for the eccentricity.
 6. The wireless power transmissionapparatus of claim 5, wherein the controller is configured to determinewhether the foreign object is present based on the first calculated loadvoltage with respect to the first reference input voltage.
 7. Thewireless power transmission apparatus of claim 6, wherein, based on theforeign object being determined present according to the firstcalculated load voltage, the controller is configured to: (i) calculatea second calculated load voltage with respect to a second referenceinput voltage and (ii) determine whether the foreign object is presentbased on the second calculated load voltage.
 8. The wireless powertransmission apparatus of claim 7, wherein, based on the firstcalculated load voltage and the second calculated load voltage beingoutside a predetermined range, the controller is configured to determinethat the foreign object is present.
 9. The wireless power transmissionapparatus of claim 7, wherein the predetermined range includes a firstrange and a second range for the first calculated load voltage and thesecond calculated load voltage, respectively, the first range and thesecond range being different from each other.
 10. The wireless powertransmission apparatus of claim 1, further comprising: an upper glassarranged to receive the target object; and an input unit configured toreceive the selection of the mode of operation.
 11. A method ofoperating a wireless power transmission apparatus for induction heating,which includes a working coil configured to change operation based onselection of a mode of operation from among a plurality of operatingmodes, the plurality of operating modes including a wireless powertransmission mode configured to wirelessly transmit power and a heatingmode configured to heat one or more objects, the method comprising:checking whether the wireless power transmission mode is selected; apreparation operation including: receiving, in the wireless powertransmission mode, a load voltage from a target object while an inverteroutput current at an operation frequency, compensating for the loadvoltage, and determining, in the wireless power transmission mode,whether a foreign object is present in the working coil based on thecompensated load voltage; and a normal mode operation includingperforming wireless power transmission at the operation frequency to thetarget object.
 12. The method of claim 11, wherein compensating for theload voltage includes compensating for the load voltage based on acurrent input voltage.
 13. The method of claim 12, wherein thepreparation operation includes: recalculating the current input voltagebased on a first reference input voltage, performing compensation forremoving variation in the load voltage with respect to the current inputvoltage, and calculating the compensated load voltage.
 14. The method ofclaim 13, wherein the preparation operation includes: compensating foran eccentricity degree between the working coil and a reception coil ofthe target object with respect to the calculated compensated loadvoltage, and calculating a first calculated load voltage based on thecompensation for the eccentricity.
 15. The method of claim 14, whereinthe preparation operation includes determining whether the foreignobject is present based on the first calculated load voltage withrespect to a first input reference voltage.
 16. The method of claim 15,wherein the preparation operation includes: based on the foreign objectbeing determined present according to the first calculated load voltage,calculating a second calculated load voltage with respect to a secondreference input voltage and determining whether a foreign object ispresent based on the second calculated load voltage.
 17. The method ofclaim 16, wherein the preparation operation includes: based on the firstcalculated load voltage and the second calculated load voltage beingoutside a predetermined range, determining that the foreign object ispresent.
 18. The method of claim 17, wherein the predetermined rangeincludes a first range and a second range for the first calculated loadvoltage and the second calculated load voltage, respectively, the firstrange and the second range being different from each other.
 19. Themethod of claim 11, wherein the preparation operation includes:calculating a deviation in the load voltage with respect to a firstreference input voltage based on data of the load voltage received fromthe target object, the data including a variation in a input voltagewith respect to a specific operation frequency, and calculating thecompensated load voltage based on a function between the deviation inthe load voltage and the input voltage.
 20. The method of claim 19,wherein the preparation operation includes: compensating for a value ofresonance current with respect to the first reference input voltage,calculating the deviation in the compensated load voltage with respectto an eccentricity degree, and calculating last load voltage accordingto a function between the compensated resonance current and thedeviation in the compensated load voltage.
 21. The method of claim 18,further comprising: based on the foreign object being determined presentin the preparation operation, providing a user alarm and stopping anoperation of the inverter.